Oil field induction generator system

ABSTRACT

An induction generator system is disclosed for utilization with an oil producing well having casing gas available at the wellhead and an existing electrical power system. An electric motor is coupled to the existing electrical power system and is utilized as a generator to drive a submersible pump or other electrical load. A gas engine which is powered by the casing gas is mechanically coupled to the electric motor by means of a drive belt and is utilized to drive the electric motor at a speed greater than the synchronous speed of the motor. While the electric motor is driven at a speed greater than its synchronous speed it will generate electrical energy which can be utilized to carry the electrical load. A novel control system is utilized to control the operation of the engine/motor generator system in response to variations in motor speeds, engine operating parameters and load/voltage conditions.

This application is a continuation of application Ser. No. 014,110,filed 2/3/87, which is a continuation of Ser. No. 881,517, filed6/30/86, which is a continuation of Ser. No. 803,513, filed 12/2/85,which is a continuation of Ser. No. 477,215, filed on 3/21/83, allabandoned.

BACKGROUND OF THE INVENTION

This invention relates to electrical power generation systems in generaland in particular to electrical power generation systems which aresuitable for utilization in oilfield applications.

In the prior art there are many methods utilized to perform the work ofremoving oil and other petrochemical deposits from pools or reservoirsbeneath the earth's surface. These methods typically include submersiblepumps, pumpjacks and other methods of lifting fluid from beneath thesurface. These devices are generally operated utilizing either electricpower from an existing electrical power distribution system or by aninternal combustion engine powered by gasoline or in some cases by thecasing gas present in the wellhead in certain wells.

Each of these known methods has its advantages and disadvantages. Forexample, electrically powered systems are generally reliable and willeffectively lift fluid from beneath the earth's surface as long aselectric power is available. However, the cost of generating electricalpower is rapidly increasing and the amount necessary to operate a largenumber of oilfield pumps can generate an extremely high utility bill.

In those applications in which casing gas is present in the wellhead, itis sometimes efficient to utilize this gas to power an internalcombustion engine to drive a pump or generator; however, the variationsin flow, pressure and availability of casing gas result in this methodbeing not a dependable source of energy. With such systems periods oflow pressure may result in downtime during which no oil is pumped fromthe well.

Therefore, there exists a need for a power generation system whichcombines the economic advantages of the gas engine system with therelative reliability of the electrical systems.

SUMMARY OF THE INVENTION

Accordingly, it is one object of the present invention to provide animproved method and apparatus for powering the removal of oil frombeneath the surface of the earth;

It is another object of the present invention to provide an inductiongenerator system which can be safely and easily operated in parallelwith an existing electrical power distribution system;

It is still another object of the present invention to provide aninduction generator system which can be powered by a gas engine fueledby casing gas from the wellhead;

It is another object of the present invention to provide an inductiongenerator system which is powered by a gas engine fueled by casing gasfrom the wellhead which can be controlled in response to variations inthe operation of the gas engine;

It is yet another object of the present invention to provide aninduction generator system which is powered by a gas engine fueled bycasing gas from the wellhead which can be controlled in response tovariations in the electrical load.

The foregoing objects are achieved as is now described. An electricmotor is coupled to the existing electrical power system and is utilizedas a generator to drive a submersible pump or other electrical load. Agas engine which is powered by the casing gas is mechanically coupled tothe electric motor by means of a drive belt and is utilized to drive theelectric motor at a speed greater than the synchronous speed of themotor. While the electric motor is driven at a speed greater than itssynchronous speed it will generate electrical energy which can beutilized to carry the electrical load. A novel control system isutilized to control the operation of the engine/motor generator systemin response to variations in motor speeds, engine operating parametersand load/voltage conditions.

BRIEF DESCRIPTION OF THE DRAWING

The novel features believed characteristic of the invention are setforth in the appended claims. The invention itself; however, as well asa preferred mode of use, further objects and advantages thereof, willbest be understood by reference to the following detailed description ofan illustrative embodiment when read in conjunction with theaccompanying drawing, wherein:

The lone FIGURE depicts a partially diagrammatic and partially schematicview of the novel induction generator system of the present invention.

DETAILED DESCRIPTION OF THE INVENTION

Referring now to the FIGURE, there is depicted a partially diagrammaticand partially schematic view of the novel induction generator system ofthe present invention.

Electric motor 10 is connected to an existing electrical powerdistribution system by means of lines 12, 14 and 16 in a manner wellknown in the art. In a preferred embodiment of the present invention,electric motor 10 is a 125 horsepower, 1800 RPM electric motormanufactured by any of a number of electric motor manufacturers. In thedepicted embodiment of the present invention, a standard lightningarrestor 18 is coupled to lines 12, 14 and 16 to protect the circuitryof the present invention from possible damage due to lightning strikes.Further, a phase monitor 20, such as the Time Mark Model No. C269 isalso coupled to lines 12, 14 and 16 to monitor the phase and voltage ofthe electrical energy present on those lines.

A gas engine 22 is mechanically coupled to electric motor 10 by means ofV-belt drive 24. In a preferred embodiment of the present invention,V-belt drive 24 utilizes sized pulleys which are chosen so that gasengine 22 will drive electric motor 10 at a speed in excess of itssynchronous speed. As is common in this art, gas engine 22 may be fueledutilizing the casing gas present at the wellhead. In many suchinstallations, this casing gas would ordinarily be vented, flared orotherwise wasted, making casing gas a very economical fuel for suchengines.

Coupled to electric motor 10, either directly or by means of a shaft, isspeed indicator 26 which is utilized in conjunction with solid statespeed sensor 28 to monitor the rotational speed of electric motor 10.This is particularly relevant, as those skilled in the electrical artwill appreciate, in that when driven at a speed in excess of itssynchronous speed, electric motor 10 will generate electrical energywhich can be utilized to carry an electrical load, such as a submersiblepump. The utilization of an induction device such as electric motor 10is particularly useful in that it will not be necessary to accuratelycontrol the frequency and voltage of motor 10, as it would be with anordinary generator. The frequency and voltage of the electrical energygenerated by overspeeding electric motor 10 will be determined by thefrequency and voltage of the existing electrical power distributionsystem, which is coupled to the stator of electric motor 10. Thus, thegas engine/electric motor generator system of the present invention maybe easily utilized to generate electrical power without the constraintsnecessary with normal generator systems. Power factor correction for theelectrical energy generated by electric motor 10 is provided utilizingcapacitors 13 and 15. The size of capacitors 13 and 15 must be chosenbased upon the amount of power utilized in a particular installation andthose ordinarily skilled in the art will appreciate that various sizedcapacitors may be utilized in this fashion.

A complex control system is utilized in conjunction with gas engine 22and electric motor 10 to ensure that the system will react to allpossible problems which might ordinarily be encountered duringoperation. The operation of gas engine 22 is monitored utilizing aMurphy Model 307PH engine "tattletale" monitoring device 30. Enginemonitoring device 30 is a standard engine monitoring device which ismanufactured by the Frank W. Murphy Company of Tulsa, Okla. and iscoupled to gas engine 22 and utilized in conjunction with control relay32. Monitoring device 30 is utilized to monitor engine faults, enginetemperatures and engine oil pressures, in a manner well known in theart. If a malfunction of gas engine 22 is detected by monitoring device30, control relay 32 is utilized to operate relay contacts 34, whichwill remove power from contactor coil 36 of electric motor 10. This isaccomplished by de-energizing control relay 38 which operates relaycontacts 40, removing power from contactor coil 36. Additionally,overload contacts 42, 44 and 46 can also be utilized to remove powerfrom contactor coil 36, which will result in electric motor 10 beingdisconnected from the existing electrical power distribution system atmotor contacts 48, 50 and 52.

Additionally, various other control relays and contacts are utilized inthe secondary circuit of transformer 54 to monitor the operation of thegas engine/electric motor generator system of the present invention.Included among these are relay contacts 56 and 58 which are operated bysolid state speed sensor 28. These relay contacts are utilized to removepower from contactor coil 36 in the event of electric motor 10increasing its speed to a level above a first selected speed, ordecreasing its speed to a level below a second selected speed. A secondcontrol relay 60 is utilized in the depicted embodiment of the presentinvention to generate a fixed time delay after the speed of electricmotor 10 has decreased to a selected level to prevent minor, temporarydrops in speed due to casing gas pressure variations from affecting thegenerator system. Relay contacts 62 are controlled by time delay controlrelay 60. As can be seen, a start button 63 can be utilized totemporarily remove relay contacts 56 and 62 from the circuit duringstartup.

Two final pairs of relay contacts are utilized to control theapplication of power to contactor coil 36. Relay contacts 64 arecontrolled by phase monitor 20 and can be utilized to remove power fromcontactor coil 36 in the event of insufficient or excessive voltage orphase related problems. Relay contacts 66 are operated by control relay68 which is utilized to monitor the existing electrical powerdistribution system. This is necessary, since a loss of power in theexisting electrical power distribution system could result in theelectrical energy being generated by this system being coupled into theexisting electrical power distribution system lines. This is a possibleshock hazard to repair crews who believe the system to be de-energized.

The final section of the novel control system of the present inventionincludes a control relay 70 which is operated in the event of relaycontacts 64 or 66 opening. Control relay 70 then operates through relaycontact 72 to operate throttle control device 74 to cause gas engine 22to slow to its idle speed. By utilizing this approach, the system may beautomatically restarted after a phase, voltage or line problem has beencorrected.

Although the invention has been described with reference to a specificembodiment, this description is not meant to be construed in a limitingsense. Various modifications of the disclosed embodiment as well asalternative embodiments of the invention will become apparent to personsskilled in the art upon reference to the description of the invention.It is therefore contemplated that the appended claims will cover anysuch modifications or embodiments that fall within the true scope of theinvention.

What is claimed is:
 1. An induction generator system for powering anelectric pump at an oil producing well having gas available at thewellhead and an existing electrical power distribution system, saidgenerator system comprising:an electrical motor coupled to an existingelectrical power distribution system and designed to rotate at aselected synchronous speed in response to application of said electricalpower; a gas engine fueled by said gas and mechanically coupled to drivesaid electrical motor at a speed in excess of said selected synchronousspeed whereby said electrical motor will generate electrical energy intoan electrical load; and, control means for coupling said existingelectrical power distribution system to said electric pump in theabsence of sufficient gas at said wellhead to drive said gas engine andfor coupling the electrical energy generated by said electrical motor tosaid existing electrical power distribution system when sufficient gasis available at said wellhead to drive said gas engine.
 2. The inductiongenerator system according to claim 1 wherein said control means furtherincludes a solid state speed sensor.
 3. The induction generator systemaccording to claim 2 wherein said control means includes means forshutting off said gas engine in response to the speed of said electricmotor exceeding a first selected speed.
 4. The induction generatorsystem according to claim 2 wherein said control means further includesmeans for shutting off said gas engine in response to the speed of saidelectric motor falling below a second selected speed.
 5. The inductiongenerator system according to claim 4 wherein said control means furtherincludes means for delaying for a particular period of time the shuttingoff of said gas engine in response to the speed of said electric motorfalling below said second selected speed.
 6. The induction generatorsystem according to claim 1 wherein said gas engine is mechanicallycoupled to said electrical motor by means of a V-belt drive.
 7. Theinduction generator system according to claim 1 wherein said controlmeans further includes means for monitoring the temperature of said gasengine.
 8. The induction generator system according to claim 1 whereinsaid control means further includes means for monitoring the state oflubrication of said gas engine.
 9. The induction generator systemaccording to claim 1 wherein said control means further includesthrottle control means coupled to said gas engine and means for causinggas engine to run at idle speed in response to the voltage generated bysaid electrical motor exceeding a first selected level.
 10. Theinduction generator system according to claim 1 wherein said controlmeans further includes throttle control means coupled to said gas engineand means for causing said gas engine to run at idle speed in responseto the voltage generated by said electrical motor falling below a secondselected level.
 11. The induction generator system according to claim 1wherein said control means further includes means for monitoring saidexisting electrical power distribution system and for shutting off saidgas engine in response to said power loss in said existing electricalpower distribution system.
 12. An induction generator system forpowering an electric load at a location where fuel is available to powera prime mover and at a location having an existing electrical powerdistribution system, said generator system comprising:an electricalmotor coupled to an existing electrical power distribution system anddesigned to rotate at a selected synchronous speed in response toapplication of said electrical power; a prime mover fueled by said fueland mechanically coupled to drive said electric motor at a speed inexcess of said selected synchronous speed whereby said electric motorwill generate electrical energy into said electric load; and, controlmeans for coupling said existing electrical power distribution system tosaid electrical load in the absence of sufficient fuel to drive saidprime mover at a speed sufficient to rotate said electric motor aboveits synchronous speed and for coupling the electrical energy generatedby said electric motor to said existing electrical power distributionsystem when sufficient fuel is available to drive said prime mover at aspeed sufficient to rotate said electric motor above its synchronousspeed, said control means includes a speed sensor adapted to monitor therotational speed of said electric motor and means to couple saidelectrical power distribution system to said electric load and means tocouple said electric motor to said electrical power distribution systemresponsive to the speed of rotation of said electric motor which issensed by said speed sensor.
 13. The induction generator systemaccording to claim 12 wherein said speed sensor is a solid state speedsensor.
 14. The induction generator system according to claim 13 whereinsaid control means includes means for shutting off said prime mover inresponse to the speed of said electric motor exceeding a first selectedspeed.
 15. The induction generator system according to claim 13 whereinsaid control means further includes means for shutting off said primemover in response to the speed of said electric motor falling below asecond selected speed.
 16. The induction generator system according toclaim 15 wherein said control means further includes means for delayingfor a particular period of time the shutting off of said prime mover inresponse to the speed of said electric motor falling below said secondselected speed.
 17. The induction generator system according to claim 12wherein said prime mover is mechanically coupled to said electric motorby means of a V-belt drive.
 18. The induction generator system accordingto claim 12 wherein said control means further includes means formonitoring the temperature of said prime mover.
 19. The inductiongenerator system according to claim 12 wherein said control meansfurther includes means for monitoring the state of lubrication of saidprime mover.
 20. The induction generator system according to claim 12wherein said control means further includes throttle control meanscoupled to said prime mover and means for causing said prime mover torun at idel speed in response to the voltage generated by said electricmotor exceeding a first selected level.
 21. The induction generatorsystem according to claim 12 wherein said control means further includesthrottle control means coupled to said prime mover for causing saidprime mover to run at idel speed in response to the voltage generated bysaid electric motor falling below a second selected level.
 22. Theinduction generator system according to claim 12 wherein said controlmeans further includes means for monitoring said existing electricalpower distribution system and for shutting off said prime mover inresponse to said power loss in said existing electrical powerdistribution system.